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From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Neil Brown <neilb@suse.de>
Cc: Jesper Juhl <jesper.juhl@gmail.com>,
	nfs@lists.sourceforge.net,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [NFS] 2.6.17.8 - do_vfs_lock: VFS is out of sync with lock manager!
Date: Mon, 21 Aug 2006 15:54:58 -0400	[thread overview]
Message-ID: <1156190098.6158.109.camel@localhost> (raw)
In-Reply-To: <17641.10665.116168.867041@cse.unsw.edu.au>

On Mon, 2006-08-21 at 13:34 +1000, Neil Brown wrote:
> Looking in fs/nfs/file.c (at 2.6.18-rc4-mm1 if it matters, but 2.6.17
> is much the same)
> 
>  - do_vfs_lock is only called when the filesystem was mounted with
>     -o nolock  EXCEPT
>  - If a lock request to the server in interrupted (when mounted with
>      -o intr) then do_vfs_lock is called to try to get the lock
>     locally.  Normally equivalent code will be called inside
>     fs/lockd/clntproc.c when the server replies that the lock has been
>     gained.  In the case of an interrupt though this doesn't happen
>     but the lock may still have happened on the server.  So we record
>     locally that the lock was gained, to ensure that it gets unlocked
>     when the process exits.
> 
> As you don't have '-o nolocks' you must be hitting the second case.
> The lock call to the server returns -EINTR or -ERESTARTSYS and
> do_vfs_lock is called just-in-case.  
> As this is a just-in-case call, it is quite possible that the lock is
> held by some other process, so getting an error is entirely possible.
> So printing the message in this case seems wrong.
> 
> On the other hand, printing the message in any other case seems wrong
> too, as server locking is not being used, so there is nothing to get
> out of sync with.
> 
> As a further complication, I don't think that in the just-in-case
> situation that it should risk waiting for the lock.
> Now maybe we can be sure there is a pending signal which will break
> out of any wait (though I'm worried about -ERESTARTSYS - that doesn't
> imply a signal does it?), but I would feel more comfortable if
> FL_SLEEP were turned off in that path.
> 
> So: Trond:  Any obvious errors in the above?
> Is the following patch ok?

Could we instead replace it with a dprintk() that returns the value of
"res"? That will keep it useful for debugging purposes.

Cheers,
  Trond


  reply	other threads:[~2006-08-21 19:55 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-08-08 14:39 Jesper Juhl
2006-08-09  5:53 ` Grant Coady
2006-08-09  8:07   ` Jesper Juhl
2006-08-10 22:37     ` Jesper Juhl
2006-08-11  0:30       ` Grant Coady
2006-08-13 23:08       ` Grant Coady
2006-08-17  6:49 ` [NFS] " Neil Brown
2006-08-17  9:58   ` Jesper Juhl
2006-08-21  3:34     ` Neil Brown
2006-08-21 19:54       ` Trond Myklebust [this message]
2006-11-21 12:43         ` Jesper Juhl
2006-11-27  9:19           ` Jesper Juhl
2007-01-29  5:08         ` Neil Brown
2007-01-29 14:16           ` Trond Myklebust
2007-01-30 23:42             ` Jesper Juhl
2007-02-01 22:39               ` Neil Brown

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